Conventional rotary pedal type bicycles have enjoyed wide usage over the years. They have the advantages of simplicity and ease of manufacture. However, they are also very restricted in their mode of operation and are limited in their capabilities. For example, let us consider a conventional ten-speed bike having a 27 inch wheel diameter, and a ratio of 3.6 revolutions of the rear wheel to 1 revolution of the pedals. Let us further assume that the ten speed bike is in high gear, and that the rider is making 60 strokes per minute with each leg, or one revolution per second of the pedals. Under these conditions the bicycle will be travelling at a speed of approximately 17.3 miles per hour or approximately 25.4 feet per second. No flexibility is provided in the application of power to the pedals. The rider must either fully rotate his legs at the rate of 60 times a minute or he cannot apply force to the rotating wheels. There is no possibility for the rider to shorten his stroke or apply brief impulses of high power to the bike. It is not possible to apply force with both legs to the two pedals simultaneously, if this should be desired. The conventional bike is therefore severely limited in its capabilities, as its mechanical limitations inflexibly dictate the mode of operation of the rider.
Accordingly, an important object of the present invention is to provide a bicycle in which the rider controls the application of power to the bike, instead of having the bike dictate the mode of application of power to it by the rider.
It is also noted with regard to conventional bicycles that the diameter of the circle through which each pedal rotates is about 13 inches. Of course, power is only applied to each pedal on the downward stroke during about 180 degrees. However, to flexibly engage the pedal during the full 360 degrees, the toe normally engages the pedal. Now, at the top of the stroke when pressure is applied downward on the pedal, no force goes into rotating the pedal; and more generally the effectiveness of the force varies as the cosine of the angle, ranging from 100% at 0 degrees (horizontal) to zero at plus and minus 90 degrees when the pedal is at the top and bottom of its stroke. At plus and minus 60 degrees, 50% of the downwardly applied force is effective; and at plus and minus 30 degrees, about 87% of the force is effectively translated into rotational torque, neglecting friction. The average effectiveness, as a result of this factor, in a conventional bike is in the order of 70 %, with 30% being lost. In addition, the need to use the toe on the pedal, to accommodate 360 degrees pedal rotation prevents fully effective application of the strength of the leg to the pedal. It is estimated that the resultant reduction in efficiency results in an additional loss of power or more than fifty percent.
Another object of the present invention is, therefore, to increase the efficiency of the application of human power to propel a bicycle.
It is also noted that the driving mechanisms of conventional 10-speed bicycles with their many sprockets and additional parts are relatively complex, having in the order of 80 or more parts. A collateral object of the present invention is to significantly reduce the complexity of variable speed or variable ratio bikes.
As will be developed in greater detail below, the present invention involves an oscillating pedal type cycle. A number of different kinds of oscillating pedal type bikes have been disclosed in the patent literature. However, it appears that the true capability of a properly designed oscillating pedal type bicycle has not been realized, as they are very rarely used, and are virtually never seen in competitive bike races. It is particularly interesting to note that two typical patents which are pertinent to the present invention, B. Ljungstrom, U.S. Pat. No. 556,545, patented Mar. 17, 1896, and British Pat. No. 28,759 of 1896, both date back to the nineteenth century. Further, these patents appear to show designs which are mechanically unsound or at least inefficient, and probably inoperative.
Accordingly, another object of the present invention is to provide a practical oscillating pedal type bicycle which is mechanically sound, which has a minimum number of parts, and minimum maintenance requirements.